Tung-Shi Huang

N-halamine biocidal coatings

Novel N-halamine siloxane and epoxide coatings are described. The coatings can be rendered biocidal by exposure to dilute bleach. Once the bound chlorine is lost from the coatings, it can be regenerated by further exposure to dilute bleach. Synthetic schemes and biocidal efficacy data are presented. The stabilities of the bound chlorine on the surfaces are also addressed. Substrates employed include sand, textiles, and paint. Potential uses for the technology are discussed.

Self-assembled antibacterial coating by N-halamine polyelectrolytes on a cellulose substrate

In this research, two N-halamine polymer precursors, a cationic homopolymer poly((3-acrylamidopropyl)trimethylammonium chloride) (CHP) and an anionic homopolymer poly(2-acrylamido-2-methylpropane sulfonic acid sodium salt) (AHP), have been successfully synthesized and coated onto cotton fabrics via a layer-by-layer (LbL) deposition technique. The coated cotton fabrics were characterized using scanning electron microscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy. The biocidal efficacies of uncoated and coated cotton fabrics were evaluated against Staphylococcus aureus and Escherichia coli. The chlorinated swatches (CHP-Cl and AHP-Cl) inactivated 100% S. aureus and 99.73% E. coli O157:H7 in 30 min. Over 51% of the chlorine is retained after the equivalent of 50 machine washes. A skin stimulation test showed that CHP-Cl and AHP-Cl compounds have no irritation to rabbit skin, and so these swatches might be utilized for biomedical applications in the future. As an easy and efficient way of coating fabrics, the LbL deposition technique can broaden the use of N-halamine biocides in other polar substances as antimicrobial functional coatings.

N-Halamine-modified antimicrobial polypropylene nonwoven fabrics for use against airborne bacteria.

Disinfecting, nonbleaching compound 1-chloro-2,2,5,5-tetramethyl-4-imidazolidinone (MC) was uniformly coated onto polypropylene melt-blown nonwoven fabrics having basis-weights of 22 and 50 g/m(2) in order to impart antimicrobial properties via a pad-dry technique. The antimicrobial efficacies of the tested fabrics loaded with MC compound were evaluated against bioaerosols of Staphylococcus aureus and Escherichia coli O157:H7 utilizing a colony counting method. It was determined that both types of coated fabrics exhibited superior antimicrobial efficacy upon exposure to aerosol generation for 3 h. The effect of the coating on air permeability was found to be minimal. Samples were stable for a 6 month time period when they were stored in darkness. However, when the fabrics were exposed to fluorescent light, partial chlorine loss was observed. The MC-coated fabrics exhibited great potential for use in protective face masks and air filters to combat airborne pathogens.

Effect of Salts of Organic Acids on Listeria monocytogenes, Shelf Life, Meat Quality, and Consumer Acceptability of Beef Frankfurters

The objective of this study was to evaluate anti-listerial efficacy of salts of organic acids, and their impact on the quality of frankfurters. Beef frankfurters were manufactured by incorporating organic acids in 5 different combinations: (1) control (no marinade addition; C); (2) sodium lactate (2% wt/wt; SL); (3) potassium lactate (2% wt/wt; PL); (4) sodium citrate (0.75% wt/wt; SC); and (5) sodium lactate (2% wt/wt)/sodium diacetate (0.25% wt/wt; SL/SD). Cooked frankfurters were inoculated with streptomycin-resistant (1500 μg/mL) L. monocytogenes (7 log₁₀ CFU/frank). Inoculated and noninoculated frankfurters were vacuum packaged and stored at 4 °C. Samples were taken weekly up to 10 wk for estimation of L. monocytogenes as well as aerobic plate count (APC) and psychrotrophs (PSY), respectively. Total of 2 independent trials of the entire experiment were conducted. Noninoculated beef frankfurters were evaluated weekly by untrained sensory panelists for 7 wk. SL, PL, and SC treatments did not (P > 0.05) adversely affect consumer acceptability through 8 wk although, SL/SD treatment was significantly (P ≤ 0.05) less preferred across all sensory attributes. SL/SD treatment negatively affected product quality, but was able to control APC, PSY, and L. monocytogenes levels. SC performed similar to the control throughout the 8, 9, and 10 wk storage periods, providing no benefit for inhibiting L. monocytogenes (increasing from 7 logs CFU/frank to 10 logs CFU/frank throughout storage) or extending shelf life of the beef frankfurters. In conclusion, 2% SL and PL, and 2% SL/0.25% SD may be effective L. monocytogenes inhibitors (maintaining inoculation levels of 7 logs CFU/frank during storage), but changes in SL/SD treatment formulation should be studied to improve product quality.

Cytocompatible antibacterial fibrous membranes based on poly(3-hydroxybutyrate-co-4-hydroxybutyrate) and quaternarized N-halamine polymer

A novel polymeric N-halamine-containing quaternary ammonium salt (PHQS) was synthesized and used to make antibacterial electrospun fibrous membranes by blending with biodegradable poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P(3HB-4HB)). The chemical structures of 3-(2′-chloroethyl)-5,5-dimethylhydantoin (CEDMH), poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) and PHQS were characterized with FT-IR, 1H NMR, 13C NMR and GPC. The obtained electrospun fibrous membranes were chlorinated with chlorine bleach and characterized by scanning electron microscopy (SEM) and thermogravimetry (TG). The new fibrous membranes provided potent antimicrobial activities against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli O157:H7. In addition, the treated electrospun fibrous membranes showed excellent stability and durability in UVA light irradiation and storage tests. The results of rat skin fibroblast cytotoxicity studies indicated that the antimicrobial membranes are biocompatible. From this research, polymeric quaternarized N-halamine antimicrobial fibrous membranes based on P(3HB-4HB) may have potential use as eco-friendly materials in food packaging and biomedicine.

Antimicrobial modification of cotton by reactive triclosan derivative

Abstract4-(4-chloro-6-(5-chloro-2-(2,4-dichloro-phenoxy)phenoxy)-1,3,5-triazin-2-ylamino)-benzenesulfonic acid sodium (CPTB), an antimicrobial agent, was synthesized from cyanuric chloride, sulfanilic acid and triclosan. The synthesized compound was coated on cotton fabrics by covalent bonds through a reactive dyeing process. The cotton fabrics coated with CPTB were characterized by FTIR and SEM. The antimicrobial properties against S. aureus and E. coli O157:H7 and the breaking strength of the treated cotton fabrics were examined before and after chlorination. The unchlorinated coated fabrics containing triclosan inactivated 95.88 % of S. aureus and 79.65 % of E. coli O157:H7 within 30 min, while the chlorinated coated samples enhanced the efficacy significantly and inactivated all S. aureus and E. coli O157:H7 within 10 min. The novel coating process in this study only caused a small degree of breaking strength loss compared with traditional pad-dry-cure coating. Washing tests and UV light tests showed that CPTB attached to cotton fabrics was very stable toward repeated washing and UVA irradiation.

N-Halamine modified thermoplastic polyurethane with rechargeable antimicrobial function for food contact surface

A polymer blend of two N-halamine precursors was prepared and homogeneously incorporated into TPU structure via a solvent casting method, and an N-halamine modified TPU film with rechargeable antimicrobial activity resulted after treating with chlorine bleach. Antimicrobial efficacies were evaluated against both Staphylococcus aureus (S. aureus) and Escherichia coli O157:H7 (E. coli). Results showed that the N-halamine modified TPU film caused 6 log CFU reduction of bacteria reduction within 2 hours of contact. Moreover, the N-halamine modified TPU displayed desirable rechargeability and stability, which maintained sufficient antimicrobial activity after 20 cycles of “discharge–recharge” process and over 4 weeks of storage. Besides, the tensile strength and surface tension of TPU were not adversely affected by N-halamine modification. The N-halamine modified TPU with rechargeable antimicrobial function exhibited great potential as a cheap, safe and effective food contact surface material for preventing food microbial cross-contamination.

Durable antimicrobial cotton fabrics treated with a novel N-halamine compound

Abstract5,5-Dimethyl-3-((3’-triethoxysilylpropylamido)propyl)hydantoin (Si-Hy), a novel N-halamine precursor, has been synthesized in this work. The traditional pad-dry-cure process was used to coat the produced Si-Hy onto cotton fabrics. The coated fabric was characterized by SEM, FTIR and XPS. After exposure to chlorine bleach, the treated fabric presented good antimicrobial ability. The chlorinated sample demonstrated potent antibacterial ability against S. aureus (ATCC 6538) and E. coli O157:H7 (ATCC 43895) in brief contact time. Sixty seven percent of oxidative chlorine was retained and over 85 % of chlorine could be recharged after storage for 15 days and rechlorination. The antibacterial materials with good biocidal efficacies have potential applications in the healthcare industry.

N-halamine modified polyester fabrics: Preparation and biocidal functions

A cyclic N-halamine precursor, 1-glycidyl-s-triazine-2,4,6-trione (GTT), was synthesized and grafted onto polyester fibers. The tricarbimide rings could be transferred to N-halamine structure upon exposure to dilute sodium hypochlorite solution. Structural and surface characterizations of the polyester (PET) fabrics treated with GTT were accomplished using FT-IR, SEM, and DSC. The antimicrobial efficacy test showed that the N-halamine modified PET could inactivate 6-log of Staphylococcus aureus (Gram-positive) and E. coli O157:H7 (Gram-negative) within 10 min of contact time. The antimicrobial fabrics exhibited good durability and stability to washing and storage.

Antimicrobial Activity of N-Halamine–Coated Materials in Broiler Chicken Houses

The antimicrobial activity of 1-chloro-2,2,5,5-tetramethyl-4-imidazoidinone (MC), a nonbleaching N-halamine compound, was investigated on materials commonly used in broiler production, including stainless steel, galvanized metal, aluminum, plastic, and pressure-treated wood. MC aqueous solutions at 0.02, 0.04, and 0.06% were challenged with Salmonella Typhimurium and Campylobacter jejuni at 6 log CFU/mL, resulting in complete inactivation of both bacteria in 30 min with 0.06% MC. Follow-up experiments were performed using test materials treated with 0.1 and 1% MC and challenged with Salmonella Typhimurium and C. jejuni at 6 log CFU per coupon. Stability of MC on the various surfaces of testing materials was assessed, and the chlorine content of the materials was measured using iodometric thiosulfate titration over a 4-week period. Antimicrobial activities were evaluated by a sandwich test on each sampling day during 4 weeks of storage. On the samples treated with 1% MC, bacteria at 6 log CFU per coupon were completely inactivated within 2 h of contact time. The antimicrobial activity extended to 4 weeks, and the active chlorine atoms in the treated materials decreased from the initial 1016 to 1015 atoms per cm2. Overall, MC had high stability and long-lasting antimicrobial activity, which suggests that MC has high potential for use as a novel antimicrobial agent to lower the microbial load on broiler house materials.